Method of recovering copper from ores.



mme ssesz 1 N0. 894,902. PATENTED AUG. 4, 1908.

. W. B. POTTER.

METHOD OF REGOVERING COPPER PROM ORES. APPLICATION FILED 'AUG. 1, 1907.

2 SHEETS-SHEET 1.

No. 894,902; PATENTED AUG. 4, 1908.

I w. BpPOTfI'ER.

METHOD OF REGOVERING COPPER FROM 0115s.

A PP LiOATION FILED AUG. I 1907.

2 SHEETS-SHEET 2.

. other than that found in the spent solution UNITED STATES PATENT our-Ion.

WILLIAM B. POTTER, OF ST. LOUIS, MISSOURI, ASSIGNOR TO ESMERALDA COPPER PRECIPI- TATING COMPANY, OFCHICAGO, ILLINOIS, A CORPORATION OF ARIZONA TERRITORY;

METHOD OF REGOVERING COPPER FROM ORES Specification oi. Letters'Patent. Application filed August 1, 1907-. Serial No. 386,581.

Patented Aug. 4, 1908. i

To all whom it may concern:

Be it known that I, WILBIAM citizen of the United States, residing at the city of St. Louis and State of Missouri, have invented certain new and useful Improvements in Methods of Recovering Copper from its Ores, of which the following is a specification, reference being had therein to the ac-.

anying drawlngs.

s invention has for 1ts object to obtain high grade metallic copper directly from its low grade. ores by aprocess'involving solution and precipitation. The process utilizes sulfur dioxid as a reagent with which to charge a'neutral solution of cupric sulfate, theprecipitation being then accomplished by sub ecting the sulfur dioXid-charged solution to proper heat and pressure. The precipitation of the copper is accom anied by the generation of free sulfuric aci (in the residual or spent liquor remaining after the precipitation of copper from the original charge solution)is used as a solvent to leach additional copper from the ore. The operations are then repeated, as before, the cupric sulfate thus prepared being charged with sulfur dioxid and subjected; to heat. and pressure, resulting in the precipitation of more copper and the re eneration of fresh quantities of being, in turn, to make more cupric sulfate. The process, accordingly, is a regenerative one in that each time cop er is precipitated largeguantie ties of free su uric acid areggenerate more than sufficient in quantity to dissolve as much copper as was previously precipitated.

The process, also, is a continuous one, and one in which the operations may be repeated indefinitely, without the use of any-solvent after each precipitation of copper. Such large quantities of free sulfuric acidare generated that there is a large excess overthat necessary to dissolve the copper, thus permitting the treatment ofcopper ores having considerable soluble angue matter, and, in the case ofores not aving soluble gangue matter sufficient to take up the free acid over and above that required for the copper, a .cheap neutralizing agent like limestone, which is available almost everywhere, can be used to dispose of such excess of acid The hereindespribed process, accordingly,can ad-' vantageously be applied to a very wide range B. POTTER, a

generative, produce and this acid" I those steps by acid, this ast-generated acid used as asolvent with which of ores having more or less soluble ingredicuts in the gangue matter, which ingredients 'would cause too great a waste of the solvent in the case of non-regenerative copper-leaching processes, or processes which, being reonly, sufficient solvent to leach the copper. In other words all, or nearly all, prior copper-leaching processes re quire either a constant replenishing of the solvent fromoutsidegsources, or, if any solvent is produced in the process, it. is onlysufficient to dissolve th co per without allowing any for soluble i I re ients in the gangue. By such prior processes, ores of copper can be treated, if any, which have a quartz or insoluble silicious gangue.

The treatment of solutions containing excess ive quantities of acid, generated incidentally in the preci itation of the co per, is hereinafter descri ed, and it is in t method, in

which the preci itation is effected, and inthe utilization oi the free acid for leachingthe proper quantity 'of copper from fresh lots of ore, that the principal points of novelty of the invention reside.

' In the drawings forming part of this specification, in which like'numbers of reference denote like parts wherever they occur, Figure 1 is a diagrammatic view of the main arts ofthe apparatus, dpartly in elevation an partly in section; an Fig. 2 is a top. plan view.

therefore, only those It should be understood, however, that, as

this invention relates primarily to a process, the apparatus shown and described is only illustrative, and. that other forms and arrangements of apparatus may be used for practicing. said process.

The ,ore from which the cop er is to be ex-' tracted is first crushed, and is t en leached or digested in any suitable receptacle (such, for example, 'as,a series of stationary lead-lined tan-ks 1, orrotating, acid-proof barrels) with dilute sulfuric acid of'about 10% strength.

The sulfuric acid required to make up that acid solution usedfor starting the recess is the only acid that must be supplied rom outside sources, and the q' uantit provided need be suflicient for leaclnng o y one round or charge of. ore. Afterward, in the regular workingof the process, the leaching of copper from the ore is done entirely with t spent-liquor or solution remaining after the recipitation of copper. Tanks 2-are used or storing leaching solutions ready to be run' into the tanks 1. The operation of leaching 110 the ore with the first acid solution in starting, and with the spent-liquor acid solutions in regular worl'ring, is the same in all cases. This leaching action, where stationary or tanks are used, is secured by passing the solution from one ore tank 1 to another until suflicient copper is leached, the weakest solution being a ways used on fresher ore and the strongest solution on ore with the least copper remaining therein. In this Way the ore is readily deprived of its copper and the leaching solution approaches neutrality, or that point at which all the free acid. is neutralized by the copper and other soluble ingredients in the ore.

The preferred manner of handling the leaching solution is as follows: Each ore tank 1 is connected with a sump tank 3 (or plurality of sump tanks) into which the solution can be run by pipes 4 after passing through the ore and after being strained by the perforated false bottom 5 of the ore tank. From this sump tank the solution can be raised and delivered by pi es 6 into the next, or any other, ore tank in t e series, and, after ercolating through the 'ore therein, it is alowed to run into its sump tank, from whence it is raised again to" any other ore tank in the series, and so on, until there has been sufficient exposure of the solution to the ore to secure for the solution the desired content of copper. By means of suitable pipe connections 7, com essed air at low pressure is a plied upon t e' surface of the solution in t e.

air-tight, covered sump tanks and the solution 1s thereby raised and delivered to any ore tank in the series, and thus the leaching of the ore can be followed throu h the tanks inany order that may be desire Ore from which the copper has been thus leached is then subjected to washing with fresh water to remove the entangled solution containing copper, after which the spent ore'is discharged into cars 1 below as tailings, and a new or fresh lot of ore charged into the ore tank. On the other hand, the solution which has taken 11 suflicient coppei if still acid, is

earnedy pipes- 8 to a tank 9 containing crushedlimestone, and the remaining free sulfuric acid is neutralized by the calcium of the limestone, this reaction ieldin calcium free acid, and due care should be taken to produce regularly a solution having the proper normal content of copper. The most suitable content of copper for the on ric sulfate solution is 6% of copper, which so ution will have a specific gravity of about 1.17, though the specific gravity of the solution will vary to some extent, depending on the nature and quantity of impurities present. It is impracticable to have the cupric sulfate 'solution contain more than 6% of copper, because in a cupric sulfate solution containing about 7% of copper the cupric sulfate begins to crystallize out. The noutral cupric sulfate solution, produced as above, is then allowed to run into lead-lined steel pressure tanks 10. These tanks are made with flanged steel covers which are bolted on, and, through a suitable pi )c 11 in the cover, compressed air at suitable pressure is plied above the surface of the solution, w 1011 pressure forces the solution through the exit pipe 12, which pipe extends from near the bottom of the tank to the top of the absorption apparatus 13, terminating in sprayers 14, causing the solution to be delivered to the top of the absorption ap mratus 13. Said apparatus comprises a large tank divided by partitions 15 into a plurality of vertical compartments 16, which partitions extend alternately from the top and the bottom of the vat 13. Through these compartments sulfur dioxid gas is forced, traveling down and up in the ser entinc path indicated by the arrows, throug 1 all the vertical compartments, finally passing out at the top of the last compartment, from which,

if any sulfur dioxid gas remains, it is delivcred th the foot of a tower of suitable construction which is filled with coke or other similar material, the gases passing upward and coming intimately in Contact .with cupric sulfate solution which trickles down from the tower top. If such a tower is used the neutral cupric sulfate solution will be delivered first to the to of the tower, will pass dowhwardly theret rough, then run from the bottom of the tower into the pressure tanks 10 to be forced through the sprayers 14 into the several compartments 16 of the main ab sorption apparatus 13. By means of such an absorption ap aratus the cupric sulfate solution is charge with an amount of sulfur dioxid e ual to 50% of the copper contained in the so ution charged. The cupric sulfate solution having thus been charged with sulfur dioxid, is run through pipe 17 into the storage tanks 18, ready for the third ste in the process, viz., the precipitation. TlllS is effected in a boiler-like tank 19 of convensupplemented with a steam jacket 1f dc- I suificient'space for the expansion of the solu- Q lution to the required heat and pressure is satisfactory results.

'to remove all the entangledspent solution.

vIt can then be producing soli sired, sufficient heating surface can bel employed and the solution thus readily heated to a temperature of-260 F'.,- while the pressure at the same time is allowed toreach 100 lbs. per square inch. 1 n i it In filling the recipitation; tank with the cupric sulfate so utionbcareishould be taken that the charge fills the tank, leaving only tion as it becomes heated, so that when expanded it will nearly if not quite fill the tank.

hen the precipitation tank, is filled in this way there is no escape of the sulfur dioxid from thesolution, and thepressure of 100 lbs. to the s uare'inchis readily developed when the so ution is heatedto the proper temperature of 260 F. Under this combination of high pressure and high temperature the reaction takes place-clearly and definitely, causing the precipitation of thirtyfive to forty per cent. of the copper in the solution as pure metallic copper, the remainder of the copper remaining in solution in the spent liquor as cupric sulfate, while, at the same time, an amount of free sulfuric acid is develo ed sufficient todissolve about two and a alf times as much cop er-as was precipitated in the'form of metal ic copperfrom the solution.

The time consumed in bringing'up the soimmaterial, efficiency and economy in the application of the heatbeing all that it is necesi l'y t0 observe. Under favorable conditions the heating may be effected in from fifteen to thirty minutes. The timeiduring which it is desirable to hold the solution under the combined heat andp'ressure depends upon the strengthof the solution, varying inversely as the strength. For a solution hav' ing approximately 'six per cent. of copper about one hour is sufii'cient to produce very Themetallic cop er, which is exceedingly pure and is in a fi rous, moss-like, spongy condition, must be washed with fresh water pressed into ingot molds, thus ingots of copperready for shipment. The copper is of suchhigh grade that it needs no refin1ng,.nor evenmelting,'to put it in ingbt form for shi ment.

v The spent solution, on .t e removal of thecopper, and after being run through pipes 20 into tanks 21 and through an ordinary filter to remove loose particles ofmetallic copper, is ready to be forced u through pi es 22 to the stock solution tans 2 in con ition'for use in leaching more ore. The solution, being still hot, will act more readily in dissolving the cop or from the ore and thus the leaching of t e ore will be expedited, and, at

with an amount of sul Y lution as be the same time, the solution, taking some hours to pass through the several ore-tanks and limestone tank for completing the neu-' tralizing of the free acid, will have an opportunity to cool downto a normal temperature so that it can be charged again with sulfur dioxid. The process thus consists of a repetition of the three essential steps or o eratlons,

-viz., leaching the ore to give the so utionthe .necessary strength of cupric sulfate, with the completion .of the neutralizing of the free acid by passing over limestone; second, charging t is neutral cupric sulfate solution urdioxid equal to about of the cop erin the solution; and third, precipitating t irty-five to forty per cent. of the copper in the'solution as pure metallic copper, leaving the solution with the remainder of the copper and a large excess of free sulfuric acid to be used again for leaching fresh char es of ore.

A modification of the above process might, in some cases, rovetmore desirable, as follows: Instead'o artly neutralizing the acid of the leaching so utidn with ore and completing the neutralizatiq'n with limestone, the whole of the neutralizingmay be effected by continued exposure of the solution to the ore, proceeding with the charging of this solution with sulfur dioxid and prec1pitating thirtyfive to forty er cent. of the copper in the sof' dre. If the ore treated does not contain enough soluble gangue matter to neutralize the freeacid, over and above that required to dissolve a new portion of copper to replace that previously precipitated, the cupric sulfate solution, kept to its normal content of 6% of copper, would with each round of o erations repeatedly increase in amountaii in time exceed the capacity of the plant to handle it. This increase is 7 about one-third with each precipitation. To

obviate this and to keep thesolutions aproximately uniform in amount and normal 1n content of copper, about two-thirds of the spent solution (instead of all of it, as in the other method herein described) is re- .turned through pipe 22 to leach ore until neutralized, and the remainder is delivered to the limestone tanks by pipes 22 and, 8 and the neutralization is effected by meansof limestone alone. The operations of charging with sulfur dioxid and precipitating under combined heat and ressure, alread described in referring to t e other metho are applied in a similar way, but separately, to t e ore -.neutralized solution, and" to the limestone-neutralized solution. To keep the solution which is neutralized with ore nor-,

mal in volume the part removed for treatment with limestone is replaced with water,

while, on the other hand, that part of the so- I lution which is neutralizedwith limestone instead of with ore, will be below the normal 6% copper content, to which it may be brought up by evaporating the excess of water. When brought to the normal content l of copper the charging with sulfur dioxid and precipitation take place in just the same manner as already described. The spent liquor from the precipitation of the limestone-neutralized solution is sent back to the limestone tanks each time for neutralizing before charging with sulfur dioxid.

By a repetition ofthe several operations of either of the two methods described all the copper is extracted and the solutions are kept regular in volume and normal in content of copper, while all the copper is precipitated, and by the same method of precipitation. The extraction of the copper from the solution is, therefore, complete, and losses are almost inappreciable.

The sulfur dioxid gas for charging solutions as above, may be obtained, in the case of treating sulfid ores, from the roasting of these ores required to change the ore from copper sulfid t o'copper oxid, which latter is very soluble in the sulfuric acid leaching solutions. The sulfur gases resulting from this roast-ing consists mainly of sulfur dioxid and thus may be utilized for charging the cupric sulfate solutions. The burning or roasting of iron pyrites may, also, in some cases serve as a convenient source of sulfur dioxid, but the usual source of supply when treating oxidized ores, such as natural oxid, carbonates, or silicates of co per, would be from the burning of sulfur. fh roasting sulfid ores of copper or iron pflyrites, one of the well known types of mu e roasting furnaces should be used in order to secure gases richer in sulfur dioxid than is obtainable from the ordinary roasting furnaces where the fuel-combustion gases are allowed to mingle with the gases resulting from the roasting of the ore. J

Any of the. well known types of sulfur burners, commonly em loyed 1n the sulfite pulp mills, is suitable or burning sulfur to produce the sulfur dioxid. In the drawings accompanying this specification no roasting furnace or sulfur burner is shown, as no particular means or method of producing sulfur dioxid is claimed in connection with the process for producing metallic copper herein described.

A notable feature in this copper-leaching process, and one ossessing decided advantages, is that, altliough the same solutions are used over and over again, with only such addition of fresh water as may be incidental to the washing of the leached ore before the latter-is discharged as tailings, and to the making up of waste naturally occurring in handling, these leaching solutions never can become foul from the repeated additions of outside soluble ingredients from the gangue of the ore, such as lime, alumina, iron, etc. All such impurities that may be dissolved as sulfate during the leaching of the ore, being ractically insoluble in neutral solutions, will e deposited in the limestone tanks or ore tanks, whenever the solutionsapproach the neutral condition. The solutions, therefore, when ready for charging with sulfur dioxid gas previous to precipitation, are of necessity clear and practically free from any of the outside im urities referred to, so that there is no possibi ity of interference with the progress of the operations, nor can the copper, when precipitated, -be contaminated y any of them, not even to a slight degree.

While this process is peculiarly and specially adapted for obtaining copper from its ores, and, hence, for the treatment of ores in which copper is the important metal to be extracted, it may be used to advantage for the treatment of ores'carrying old and silver as well. In the latter case, a ter the copper has been extracted by this process, the residual ores or tailings are in a condition especially favorable for the application of wellknown methods, such as cyanidation, chlorination, or amalgamation, for the saving of the precious metals, thus permitting a more com lete extraction of the latter and at muc lower cost than if the ores had not been previously treated for obtaining the copper.

Havingthus described my said invention, what I claim and desire to secure by Letters- Patent is:

1. The herein-described process of recoverin copper from its ores, which consists in leaching the ore with reagent suitable to form a neutral cupric sulfate solution, charging the solution with sulfur dioxid, and, thereafter, heating said solution to a temperature of approximately 260 Fahrenheit, and subjecting same to a pressure of approximately 100 pounds per square inch.

2. The herein-described process of recovering copper from its ores, which consists in leaching the ore with reagent suitable to form a neutral cupric sulfate solution, charging the solution with sulfur dioxid, heating said solution to a temperature of approximately 260 Fahrenheit, subjecting same to a pressure of ap roximately 100 pounds per square inch, an subse uently neutralizing the excess of sulfuric aci formed.

3. The herein-described process of recovering copper from its ores, which consists in leaching the ore with reagent suitable to form a neutral cupric sulfate solution, charg ing the solution with sulfur dioxid, heating said solution to a temperature of approximately 260 Fahrenheit, subjecting same to a pressure of ap roximately 100 pounds per square inch, an subse uently neutralizing the excess of sulfuric acid formed as fast as generated;

' 4. The herein-described process of recovcopper from its ores, which consists in leaching the ore with reagent suitable to form a neutral cupric sulfate solution, charging the solution w1th sulfur dioxid, and, thereafter, simultaneously heating said solution to a temperature of approximately 260 Fahrenheit, and subjecting same to a pressure of approximately 100 pounds per square inch.

5. The herein-described process of recoverin copper from its ores, which consists in leac ing the ore with reagent suitable to form a cupric sulfate solution, any free acid remaining being neutralized by contact with limestone or other suitable materiahcharging the resulting neutral cupric sulfate solu-.

tion with sulfur dioxid, and, thereafter, heatin said solution sufficiently high above the boiling point and under pressure-suited for the precipitation of metallic copper, using highabove the boiling point and under pres-- sure suited for the precipitation of metallic copper, using a part of the resultin spent solution with its content of free acid for dissolvin copper from a new lot of ore until neutra for a new preci itation-of metallic copper under suitable eat and pressure after chargin with sulfur dioxid, and neutralizing the. rec sulfuric acid in the remainder of the spent solution, evaporating said neutralized solution to original strength charging, with sulfur dioxid, and precipitating metallic cop er therefrom by applying suitable heat an pressure.

7. The herein-described process of recovering copper from its ores, which consists in leaching the ore with reagent suitable to form a neutral cupric sulfate solution, charging the solution with sulfur dioxid, and, thereafter, heatin the solution sufiiciently high above the boi ing point and under pressure suited for the precipitation of metallic copper, and neutralizing all of the free sulfuric acid contained in the spent solution, evaporating the thus neutralized solution to original strength, charging same with sulfur dioXid, and preci itating metallic copper therefrom by app ying suitable heat and pressure thereto.

8. The herein-described process of recovering copplfr from its ores, which consists in leaching t e ores with a reagent suitable to form a'neutral cupric sulfate solution, charging the solution With sulfur dioxid, and,

thereafter, heatin the solution sufliciently high above the boi l sure suited for the recipitation of metallic coEper, and neutra lzing a part of the free su uric acid contained in the spent solution,- evaporating the thus neutralized solution to origlnal strength, charging same with sulfur ing point and under presdioxid, and preci itating metallic copper therefrom by app ying' suitable heat .and pressure thereto.

In testimony whereof I have aflixed my signature in presence of two witnesses.

WILLIAM B. POTTER. 

